CN116137223A - Zoned non-uniform field photoionization and/or photochemical ionization source - Google Patents

Zoned non-uniform field photoionization and/or photochemical ionization source Download PDF

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CN116137223A
CN116137223A CN202111374926.3A CN202111374926A CN116137223A CN 116137223 A CN116137223 A CN 116137223A CN 202111374926 A CN202111374926 A CN 202111374926A CN 116137223 A CN116137223 A CN 116137223A
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electrode
ion
ionization
ionization source
hole
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李海洋
万宁波
花磊
蒋吉春
谢园园
李函蔚
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Dalian Institute of Chemical Physics of CAS
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Dalian Institute of Chemical Physics of CAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/107—Arrangements for using several ion sources
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/06—Electron- or ion-optical arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/14—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers
    • H01J49/145—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers using chemical ionisation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/16—Ion sources; Ion guns using surface ionisation, e.g. field-, thermionic- or photo-emission
    • H01J49/161—Ion sources; Ion guns using surface ionisation, e.g. field-, thermionic- or photo-emission using photoionisation, e.g. by laser

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  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Electron Tubes For Measurement (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

Abstract

The invention relates to a mass spectrometry instrument, in particular to a zonal heterogeneous field photoionization and/or photochemical ionization source device capable of realizing full ionization of a reagent, which comprises an ultraviolet light source, an ion repulsion electrode, an isolation electrode, an ion transmission electrode, an ion focusing electrode, an ionization source outlet electrode, a sample injection capillary, a side pumping valve and an ionization source cavity; the ion repulsion electrode, the isolation electrode, the ion transmission electrode, the ion focusing electrode and the ionization source outlet electrode are all arranged in the ionization source cavity in parallel, insulated and coaxial, wherein the isolation electrode and the ion focusing electrode divide the ionization region into three chambers which are respectively a reagent ion generation region, an ion molecule reaction region and an ion focusing region. The rapid switching of photoionization or photochemical ionization can be achieved by varying the electric field strength of the reagent ion generating region. The isolating electrode is a convex electrode with a central through hole and an edge thickness of 1-10mm, and the influence of sample gas reflux on the ionization process of the reagent molecules can be effectively avoided by increasing the thickness of the isolating electrode and properly reducing the size of the central through hole; and secondly, 1 or more than 1 ion transmission electrode is added in the reagent ion generation area, so that reagent molecules can be fully ionized to generate high-strength and high-purity reagent ions, and the sensitivity of the analysis of the to-be-detected object is effectively improved. The device can be used with any type of mass analyzer to realize high-sensitivity and rapid detection of various trace volatile components.

Description

Zoned non-uniform field photoionization and/or photochemical ionization source
Technical Field
The invention relates to a mass analyzer, in particular to an ionization source of a mass spectrometer, and specifically relates to a partitioned high-sensitivity photoionization and/or photochemical ionization source capable of realizing full ionization of reagent molecules.
Background
The basic principle of mass spectrum is that each component in a sample to be measured is ionized in an ion source to generate ions with different mass-to-charge ratios, then ion beams with different initial speeds are formed under the action of an ion guiding or accelerating electric field, the ions enter a mass analyzer, a mass separation process is completed by utilizing the electric field or a magnetic field, a mass spectrogram is obtained, and element composition information of each component in the sample to be measured is reversely deduced from the mass spectrogram according to the measured mass-to-charge ratios. The mass spectrum technology has the advantages of high sensitivity, high analysis speed, easy analysis of spectrograms, wide range of analyzable compound types and the like, and is widely applied to the rapid on-line detection of complex mixed samples. The ion source is one of the core components of the mass spectrum, is responsible for ionization of the sample, and is closely related to the achievable sensitivity of the mass spectrum. Ultraviolet light ionization is a high-efficiency 'soft' ionization technology, which is a threshold ionization technology, and after the molecules of an object to be detected absorb photons, only the molecules of a compound with ionization energy (Ionization energy, IE) lower than the photon energy are ionized. Because photon energy absorbed by the molecule of the object to be detected is only slightly higher than ionization energy thereof, a large amount of molecular ions are generated by photoionization, and the photon energy is combined with a mass analyzer, so that the photon energy can be used for rapid online qualitative and quantitative analysis of complex samples [ Chinese patent invention: 201611039752.4]. The highest energy capable of transmitting photons is 11.8eV at present due to the material of the light window, and the compound with ionization energy higher than 11.8eV (such as methane, IE=12.61 eV, acetonitrile, IE=12.2 eV and the like) cannot be effectively ionized, so that the application field of the photoionization source mass spectrum is limited. Photochemical ionization is another highly efficient "soft" ionization technique, whose principle is: firstly, selecting a reagent gas according to the property of a sample to be detected, generating high-strength reagent ions through photoionization or photoelectron ionization, and then carrying out ionic molecular reaction on the reagent ions and sample molecules to realize ionization of the molecules of the object to be detected [ Chinese patent invention: 201811381275.9, the photochemical ionization produces few fragment ions, has simple mass spectrogram and has higher sensitivity. Photochemical ionization enables a variety of ionic molecular reactions, including: proton transfer, charge transfer, electrophilic addition, anion extraction, etc., the analytes of different characteristics can be effectively ionized by means of different types of ionic molecular reactions. However, typically the reagent ion generating region and the analyte ionization region are not strictly zoned, which allows the sample gas to flow back to the reagent ion generating region, and substrates in the sample, such as humidity, can have an effect on the ionization of the reagent ions, and thus on the sensitivity of photochemical ionization.
Therefore, the invention designs a non-uniform field photoionization and/or photochemical ionization source capable of realizing the full photoionization of reagent molecules, and based on a single ultraviolet light source, the chemical ionized reagent ions are obtained by photoionization or photoelectron ionization, and different reagent ions can be obtained by changing the types of reaction gases; by the unique design of the isolating electrode structure, the independent ionization of the reagent gas is realized, and the influence of the sample gas reflux on the ionization process of the reagent ions is reduced; secondly, in the reagent ion generating region, one or more than one transport ionization is additionally added, so that sufficient photoionization of reagent molecules is realized, and reagent ions with high intensity and high purity are generated.
Disclosure of Invention
The invention aims to provide a zoned non-uniform field photoionization and/or photochemical ionization source capable of realizing full photoionization of reagent molecules, which is used for realizing rapid switching of different reagent ions based on a single ultraviolet light source so as to widen the range of ionizable and detected samples; by the unique design of the isolating electrode structure, the independent ionization of the reagent gas is realized, and the influence of the sample gas reflux on the ionization process of the reagent ions is reduced; secondly, in the reagent ion generating region, one or more than one transport ionization is additionally added, so that sufficient photoionization of reagent molecules is realized, and reagent ions with high intensity and high purity are generated.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the utility model provides a subregion inhomogeneous field photoionization and/or photochemistry ionization source device, includes ultraviolet light source, reaction gas sampling tube, sample gas sampling tube, ionization source cavity, its characterized in that: the ionization source cavity is a hollow airtight cavity, a through hole is arranged at the top of the ionization source cavity, a light window of the ultraviolet light source penetrates through the through hole and extends into the ionization source cavity, and the ultraviolet light source is in airtight connection with the through hole;
an ion repulsion electrode, an ion transmission electrode, an isolation electrode, an ion transmission electrode, an ion focusing electrode and an ionization source outlet electrode are sequentially arranged in the ionization source cavity along the emergent direction of an ultraviolet light beam emitted by an ultraviolet light source; the electrodes are of circular ring structures with through holes in the middle, and are arranged in parallel at intervals through annular insulating gaskets with through holes in the middle, and the electrodes and the through holes of the insulating gaskets are coaxial; the insulating gasket is connected with the adjacent electrode plates in a sealing way;
the lower opening end of the central through hole of the isolation electrode is provided with a convex electrode which is coaxial with the through hole and protrudes annularly, so that the backflow of sample gas can be effectively avoided, and the ionization of reagent ions is influenced; the ultraviolet light beam passes through each electrode through hole along the axial direction of the electrode;
the outlet electrode (6) may also be referred to as a Skimmer 1 electrode, a Sampler electrode;
the isolation electrode and the ion focusing electrode divide an ionization region between the ion repulsion electrode and the outlet electrode into three chambers along the emergent direction of the ultraviolet light beam, which are respectively: a reagent ion generating region located between the repeller electrode and the separator electrode, an ion molecule reacting region located between the separator electrode and the ion focusing electrode, and an ion focusing region located between the ion focusing electrode and the ionization source outlet electrode;
the reaction gas sample injection tube passes through the outer wall surface of the ionization source cavity, the gas outlet end of the reaction gas sample injection tube stretches into the reagent ion generation region, the outlet end faces the separation region between the repulsion electrode and the ion transmission electrode plate close to the repulsion electrode, the gas outlet end of the reaction gas sample injection tube faces the ultraviolet light beam irradiation region, the reaction gas generates reagent ions or sample ions in the ultraviolet light beam irradiation region, the reagent ions or sample ions enter the ion molecule reaction region through the middle through hole of the separation electrode, and the gas inlet end of the reaction gas sample injection tube is connected with a reaction gas source or a sample gas source;
the sample gas sampling pipe penetrates through the outer wall surface of the ionization source cavity, the gas outlet end of the sample gas sampling pipe extends into the ion molecule reaction zone, the outlet end faces the isolation electrode and the interval zone between the ion transmission electrode plates close to the isolation electrode, the gas outlet end of the sample gas sampling pipe faces the side wall surface of the annular protrusion, and the gas inlet end of the sample gas sampling pipe is connected with a sample gas source; generating sample ions in an ion molecule reaction zone;
a through hole A is arranged at the bottom of the ionization source cavity, and an ionization source outlet electrode is connected with the bottom of the ionization source cavity in a sealing way; the circular through hole of the ionization source outlet electrode is arranged corresponding to the through hole A, namely sample ions pass through the circular through hole of the ionization source outlet electrode and the through hole A to leave the ionization source cavity;
the side wall of the ionization source cavity is provided with a gas outlet, the gas outlet is connected with an air extraction valve through a vacuum pipeline, and the other end of the side extraction valve is connected with a vacuum pump through a vacuum pipeline.
The axial height of the annular protrusion is 0.8-9.8mm, the lower end face of the annular protrusion is positioned above the plane A of the upper surface of the pole piece of the ion transmission electrode close to the lower part of the isolation electrode, and the distance between the lower end face of the annular protrusion and the plane A is 0.2-9.2mm.
The reagent ion generating region is provided with 1 or more than 2 ion transmission electrodes in order to fully ionize reagent molecules with light to generate reagent ions of high intensity and high purity;
the ultraviolet light source is a gas discharge lamp light source, a laser light source or a synchronous radiation light source.
And a through hole or a groove which is used as a gas outlet and penetrates through the inner wall and the outer wall of the insulating sheet is formed in the radial direction of the middle through hole on the insulating sheet between the ion focusing electrode and the ionization source outlet electrode.
The ion repulsion electrode, the ion transmission electrode, the isolation electrode, the ion transmission electrode and the ion focusing electrode are made of stainless steel plates with the thickness of 0.5-10mm, and the inner diameter of the central through hole is 0.5-16mm; the outlet electrode of the ionization source is a conical stainless steel plate with a central aperture of 1mm, and the distance between two adjacent electrode plates is 1-10mm;
the repulsive electrode and the adjacent ion transmission electrode, the isolation electrode and the adjacent ion transmission electrode are divided by resistors with the resistance value of 1-2MΩ; the reagent ion generation area is provided with 1 or more than 2 ion transmission electrodes, and the voltage between the more than 2 ion transmission electrodes is divided by a resistor with the resistance value of 1-2MΩ;
the ion repulsion electrode and the isolation electrode are respectively loaded with the same or different voltages, the voltage loaded on the ion repulsion electrode is greater than or equal to the voltage loaded on the isolation electrode, the ion focusing electrode and the ionization source outlet electrode are sequentially loaded with different voltages in sequence from high to low, ion transmission gradient electric fields with different intensities are formed from top to bottom in the axial direction of the central area of each electrode through hole, ions are focused and transmitted towards the middle through hole of the ionization source outlet electrode, and the size of the ion transmission gradient electric field is 0-300V/cm.
The through hole in the middle of the ionization source outlet electrode is an ion outlet small hole, and the electrode is connected with an ion inlet of the mass analyzer; the mass analyzer is one of a quadrupole mass analyzer, an ion trap mass analyzer, a magnetic mass analyzer and a time-of-flight mass analyzer or a combination of more than 2 of the mass analyzers.
The air pressure in the ionization source cavity is 10 -3 -10 5 Pa；
An electric heating element and/or an insulating layer are arranged on the outer walls of the pipelines of the reaction gas sampling pipe and the sample gas sampling pipe, and the temperature of the reaction gas and the sample gas entering the ionization region can be controlled between room temperature and 300 ℃.
The reaction gas sampling tube and the sample gas sampling tube can be a metal capillary or a quartz capillary respectively, and can be one or more than one; the length is 0.05-5 m, and the inner diameter is 25-500 mu m.
The ionization source can work in two modes of photochemical ionization and photoionization, and can realize mutual switching by changing the voltage loaded on the repulsive ionization, the isolating electrode and the ion focusing electrode and the type of the reaction gas.
The outer wall surface of the ultraviolet light source is in airtight connection with the inner wall surface of the through hole, and the peripheral edge of the ionization source outlet electrode is in airtight connection with the inner wall surface of the through hole A;
the reaction gas provided by the reaction gas source is one or more than two gases of nitrogen, argon, helium or other rare gases with mass purity of more than 99.999 percent, and one or more than two gases of water vapor, dichloromethane, dibromomethane, oxygen and nitric oxide are carried.
The method has the advantages that:
1. compared with photoionization and/or photochemical ionization sources capable of realizing focusing in the sources, 1 or more than 2 transmission electrodes are added in the reagent ion generation area, so that reagent molecules can be fully photoionization; secondly, the structure of the isolation electrode is improved, so that the influence of sample gas reflux on the ionization process of the reagent can be effectively reduced.
The two modes of photoionization and chemical ionization can be rapidly diced, and reagent ions are flexible and changeable, so that the variety of ionizable volatile organic compounds is widened.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 shows the humidity of the sample gas before and after the isolation electrode is increased to CH 2 Br 2 + Influence of ionization of reagent ions.
Detailed Description
Please refer to fig. 1, which is a schematic diagram of the structure of the present invention. The invention relates to a zoned nonuniform field photoionization and/or photochemical ionization source device, which comprises an ultraviolet light source 1, a reaction gas sample injection tube 7, a sample gas sample injection tube 8 and an ionization source cavity 9, and is characterized in that: the ionization source cavity 9 is a hollow closed cavity, a through hole is arranged at the top of the ionization source cavity 9, a light window of the ultraviolet light source 1 penetrates through the through hole and extends into the ionization source cavity 9, and the ultraviolet light source 1 is in closed connection with the through hole;
an ion repulsion electrode 2, an ion transmission electrode 4, an isolation electrode 3, an ion transmission electrode 4, an ion focusing electrode 5 and an ionization source outlet electrode 6 are sequentially arranged in the ionization source cavity 9 along the emergent direction of an ultraviolet light beam emitted by the ultraviolet light source 1; the electrodes are of circular ring structures with through holes in the middle, and are arranged in parallel at intervals through annular insulating gaskets with through holes in the middle, and the electrodes and the through holes of the insulating gaskets are coaxial; the insulating gasket is connected with the adjacent electrode plates in a sealing way;
the lower opening end of the central through hole of the isolation electrode 3 is provided with a convex electrode which is coaxial with the through hole and protrudes annularly, so that the backflow of sample gas can be effectively avoided, and the ionization of reagent ions is influenced; the ultraviolet light beam passes through each electrode through hole along the axial direction of the electrode;
the isolation electrode 3 and the ion focusing electrode 5 divide the ionization region between the ion repulsion electrode 2 and the outlet electrode 6 into three chambers along the emergent direction of the ultraviolet light beam, which are respectively: a reagent ion generating region 15 located between the repeller electrode 2 and the separator electrode 3, an ion molecule reacting region 16 located between the separator electrode 3 and the ion focusing electrode 5, and an ion focusing region 17 located between the ion focusing electrode 5 and the ionization source outlet electrode 6;
the reaction gas inlet pipe 7 passes through the outer wall surface of the ionization source cavity 9, the gas outlet end of the reaction gas inlet pipe extends into the reagent ion generation area 15, the outlet end faces the interval area between the repulsion electrode 2 and the electrode plate of the ion transmission electrode 4 close to the repulsion electrode 2, the gas outlet end of the reaction gas inlet pipe is arranged towards the ultraviolet light beam irradiation area, the reaction gas generates reagent ions or sample ions in the ultraviolet light beam passing area, the reagent ions or sample ions pass through the middle through hole of the isolation electrode 3 and enter the ion molecule reaction area 16, and the gas inlet end of the reaction gas inlet pipe 7 is connected with the reaction gas source 12 or the sample gas source 13;
the sample gas inlet pipe 8 passes through the outer wall surface of the ionization source cavity 9, the gas outlet end of the sample gas inlet pipe extends into the ion molecule reaction zone 16, the outlet end faces the spacing area between the isolation electrode 3 and the ion transmission electrode 4 polar plate close to the isolation electrode 3, the gas outlet end of the sample gas inlet pipe 8 faces the annular protruding side wall surface, and the gas inlet end of the sample gas inlet pipe is connected with the sample gas source 13; generating sample ions in the ion molecule reaction zone 16;
a through hole A is arranged at the bottom of the ionization source cavity 9, and the ionization source outlet electrode 6 is connected with the bottom of the ionization source cavity 9 in a sealing way; the circular through hole of the ionization source outlet electrode 6 is arranged corresponding to the through hole A, namely, sample ions pass through the circular through hole and the through hole A of the ionization source outlet electrode 6 to leave the ionization source cavity 9;
a gas outlet is arranged on the side wall of the ionization source cavity 9, the gas outlet is connected with an air extraction valve 10 through a vacuum pipeline, and the other end of the side extraction valve is connected with a vacuum pump 11 through a vacuum pipeline.
The axial height of the annular protrusion is 0.8-9.8mm, the lower end face of the annular protrusion is positioned above the plane A of the upper surface of the pole piece of the ion transmission electrode close to the lower part of the isolation electrode, and the distance between the lower end face of the annular protrusion and the plane A is 0.2-9.2mm.
The reagent ion generating region 15 is provided with 1 or more than 2 ion transfer electrodes 4 in order to fully ionize reagent molecules with light to generate reagent ions of high intensity and high purity;
the ultraviolet light source 1 is a gas discharge lamp light source, a laser light source or a synchrotron radiation light source.
Through holes or grooves penetrating through the inner wall and the outer wall of the insulating sheet as gas outlets are formed in the radial direction of the middle through holes on the insulating sheet between the ion focusing electrode 5 and the ionization source outlet electrode 6.
The ion repulsion electrode 2, the ion transmission electrode 4, the isolation electrode 3, the ion transmission electrode 4 and the ion focusing electrode 5 are made of stainless steel plates with the thickness of 0.5-10mm, and the inner diameter of the central through hole is 0.5-16mm; the ionization source outlet electrode 6 is a conical stainless steel plate with a central aperture of 1mm, and the distance between two adjacent electrode plates is 1-10mm;
the repulsive electrode 2 and the adjacent ion transmission electrode 4, the isolating electrode 3 and the adjacent ion transmission electrode 4 are divided by resistors with resistance value of 1-2MΩ; the reagent ion generating region 15 is provided with 1 or more than 2 ion transmission electrodes 4, and the voltage between the more than 2 ion transmission electrodes is divided by a resistor with the resistance value of 1-2MΩ;
the ion repulsion electrode 2 and the isolation electrode 3 are respectively loaded with the same or different voltages, the ion repulsion electrode 2 is loaded with the voltages which are greater than or equal to the voltages loaded on the isolation electrode 3, the ion focusing electrode 5 and the ionization source outlet electrode 6 are sequentially loaded with the different voltages from high to low, ion transmission gradient electric fields with different intensities are formed from top to bottom in the axial direction of the central area of each electrode through hole, ions are focused and transmitted towards the middle through hole of the ionization source outlet electrode 6, and the size of the ion transmission gradient electric fields is 0-300V/cm.
The middle through hole of the ionization source outlet electrode 6 is an ion outlet small hole, and the electrode is connected with the ion inlet of the mass analyzer 18; the mass analyzer 18 is one of a quadrupole mass analyzer, an ion trap mass analyzer, a magnetic mass analyzer, a time-of-flight mass analyzer, or a combination of any 2 or more of the above mass analyzers.
The reaction gas sample tube 7 and the sample gas sample tube 8 can be a metal capillary or a quartz capillary respectively, and can be one or a plurality of reaction gas sample tubes; the length is 0.05-5 m, and the inner diameter is 25-500 mu m.
The ionization source can work in two modes of photochemical ionization and photoionization, and can realize mutual switching by changing the voltages loaded on the repulsive ionization 2, the isolating electrode 3 and the ion focusing electrode 5 and the types of the reaction gases.
The outer wall surface of the ultraviolet light source 1 is in airtight connection with the inner wall surface of the through hole, and the peripheral edge of the ionization source outlet electrode 6 is in airtight connection with the inner wall surface of the through hole A;
the reaction gas provided by the reaction gas source 12 is one or more than two gases of nitrogen, argon, helium or other rare gases with mass purity of more than 99.999 percent, and one or more than two gases of water vapor, dichloromethane, dibromomethane, oxygen and nitric oxide are carried.
In the specific implementation, the electric heating element and/or the heat preservation layer 14 are arranged on the outer walls of the pipelines of the protective gas sampling pipe 7 and the sample gas sampling pipe 8, so that the temperature of the gas entering the ionization region can be controlled to be between room temperature and 300 ℃, and the heated gas can effectively avoid the adsorption and precipitation of gas molecules on the inner wall of the sampling pipeline. Different voltages are sequentially loaded on the ion repulsion electrode 2, the ion acceleration electrode 3, the ion focusing electrode 5 and the ionization source outlet electrode 6 from high to low, ion transmission gradient electric fields with different intensities are formed from top to bottom in the axial direction of the central area of each electrode through hole, so that ions are focused and transmitted towards the middle through hole of the ionization source outlet electrode 6, and the size of the ion transmission gradient electric field is 0-300V/cm. The opening and closing degree of the side-pumping valve 10 connected with the gas outlet on the side wall of the ionization region cavity 9 is adjusted, but the working gas pressure of the ionization region cavity 9 is conveniently adjusted within the range of 10-1000Pa, so that high-efficiency photoionization and/or photochemical ionization under different gas pressures and modes can be realized. By CH 2 Br 2 Photoionization of the reagent gas is exemplified as shown in FIG. 2, which shows the sample pairs CH with different humidities 2 Br 2 + Influence of ionization of reagent ions, CH in ionization source improved after addition of isolation electrode 3 compared with photoionization source without addition of isolation electrode 3 2 Br 2 + The photoionization process of the reagent ions is significantly reduced by the influence of the humidity of the sample gas.

Claims (10)

1. The utility model provides a subregion inhomogeneous field photoionization and/or photochemistry ionization source device, includes ultraviolet light source (1), reaction gas sampling tube (7), sample gas sampling tube (8), ionization source cavity (9), its characterized in that: the ionization source cavity (9) is a hollow airtight cavity, a through hole is formed in the top of the ionization source cavity (9), a light window of the ultraviolet light source (1) penetrates through the through hole and extends into the ionization source cavity (9), and the ultraviolet light source (1) is connected with the through hole in an airtight mode;
an ion repulsion electrode (2), an ion transmission electrode (4), an isolation electrode (3), an ion transmission electrode (4), an ion focusing electrode (5) and an ionization source outlet electrode (6) are sequentially arranged in the ionization source cavity (9) along the emergent direction of an ultraviolet light beam emitted by the ultraviolet light source (1); the electrodes are of circular ring structures with through holes in the middle, and are arranged in parallel at intervals through annular insulating gaskets with through holes in the middle, and the electrodes and the through holes of the insulating gaskets are coaxial; the insulating gasket is connected with the adjacent electrode plates in a sealing way;
the lower opening end of the central through hole of the isolation electrode (3) is provided with a convex electrode which is coaxial with the through hole and protrudes annularly, so that the backflow of sample gas can be effectively avoided, and the ionization of reagent ions is influenced; the ultraviolet light beam passes through each electrode through hole along the axial direction of the electrode;
the isolation electrode (3) and the ion focusing electrode (5) divide an ionization region between the ion repulsion electrode (2) and the outlet electrode (6) into three chambers along the emergent direction of ultraviolet light beams, which are respectively: a reagent ion generating region (15) located between the repeller electrode (2) and the separator electrode (3), an ion molecular reaction region (16) located between the separator electrode (3) and the ion focusing electrode (5), and an ion focusing region (17) located between the ion focusing electrode (5) and the ionization source outlet electrode (6);
the reaction gas sampling tube (7) passes through the outer wall surface of the ionization source cavity (9) and the gas outlet end of the reaction gas sampling tube stretches into the reagent ion generation region (15), the outlet end faces the separation region between the repulsion electrode (2) and the electrode plate of the ion transmission electrode (4) close to the repulsion electrode (2), the gas outlet end of the reaction gas sampling tube is arranged towards the ultraviolet beam irradiation region, the reaction gas generates reagent ions or sample ions in the ultraviolet beam irradiation region, the reagent ions or sample ions pass through the middle through hole of the isolation electrode (3) and enter the ion molecule reaction region (16), and the gas inlet end of the reaction gas sampling tube (7) is connected with the reaction gas source (12) or the sample gas source (13);
the sample gas sampling tube (8) passes through the outer wall surface of the ionization source cavity (9) and the gas outlet end of the sample gas sampling tube stretches into the ion molecule reaction zone (16), the outlet end faces the separation area between the isolation electrode (3) and the electrode plate of the ion transmission electrode (4) close to the isolation electrode (3), the gas outlet end of the sample gas sampling tube is arranged towards the side wall surface of the annular protrusion, and the gas inlet end of the sample gas sampling tube (8) is connected with the sample gas source (13); generating sample ions in an ion molecule reaction zone (16);
a through hole A is arranged at the bottom of the ionization source cavity (9), and an ionization source outlet electrode (6) is connected with the bottom of the ionization source cavity (9) in a sealing way; the circular through hole of the ionization source outlet electrode (6) is arranged corresponding to the through hole A, namely, sample ions pass through the circular through hole and the through hole A of the ionization source outlet electrode (6) and leave the ionization source cavity (9);
the side wall of the ionization source cavity (9) is provided with a gas outlet, the gas outlet is connected with an air extraction valve (10) through a vacuum pipeline, and the other end of the side extraction valve is connected with a vacuum pump (11) through a vacuum pipeline.
2. The apparatus according to claim 1, wherein:
the axial height of the annular protrusion is 0.8-9.8mm, the lower end face of the annular protrusion is positioned above the plane A of the upper surface of the pole piece of the ion transmission electrode close to the lower part of the isolation electrode, and the distance between the lower end face of the annular protrusion and the plane A is 0.2-9.2mm.
3. The apparatus according to claim 1, wherein:
the reagent ion generating region (15) is provided with 1 or more than 2 ion transfer electrodes (4) in order to fully ionize reagent molecules with light to generate reagent ions of high intensity and high purity;
the ultraviolet light source (1) is a gas discharge lamp light source, a laser light source or a synchronous radiation light source.
4. The apparatus according to claim 1, wherein:
and a through hole or a groove which is used as a gas outlet and penetrates through the inner wall surface and the outer wall surface of the insulating sheet is formed in the radial direction of the middle through hole on the insulating sheet between the ion focusing electrode (5) and the ionization source outlet electrode (6).
5. The apparatus according to claim 1, wherein:
the ion repulsion electrode (2), the ion transmission electrode (4), the isolation electrode (3), the ion transmission electrode (4) and the ion focusing electrode (5) are made of stainless steel plates with the thickness of 0.5-10mm, and the inner diameter of the central through hole is 0.5-16mm; the ionization source outlet electrode (6) is a conical stainless steel plate with a central aperture of 1mm, and the distance between two adjacent electrode plates is 1-10mm;
the repulsive electrode (2) and the adjacent ion transmission electrode (4) and the isolating electrode (3) and the adjacent ion transmission electrode (4) are divided by resistors with the resistance value of 1-2MΩ; the reagent ion generation area (15) is provided with 1 or more than 2 ion transmission electrodes (4), and the resistance voltage division between the more than 2 ion transmission electrodes is 1-2MΩ;
the ion repulsion electrode (2) and the isolation electrode (3) are respectively loaded with the same or different voltages, the ion repulsion electrode (2) is loaded with the voltages which are greater than or equal to the voltages loaded on the isolation electrode (3), the ion focusing electrode (5) and the ionization source outlet electrode (6) are sequentially loaded with the different voltages from high to low, ion transmission gradient electric fields with different intensities are formed from top to bottom in the axial direction of the central area of each electrode through hole, ions are focused and transmitted towards the middle through hole of the ionization source outlet electrode (6), and the size of the ion transmission gradient electric field is 0-300V/cm.
6. The apparatus according to claim 1, wherein:
the middle through hole of the ionization source outlet electrode (6) is an ion outlet small hole, and the electrode is connected with the ion inlet of the mass analyzer (18); the mass analyzer (18) is one of a quadrupole mass analyzer, an ion trap mass analyzer, a magnetic mass analyzer and a time-of-flight mass analyzer or a combination of more than 2 of the mass analyzers.
7. The apparatus according to claim 1, wherein:
the internal air pressure of the ionization source cavity (9) is 10 -3 -10 5 Pa；
An electric heating element and/or a heat preservation layer (14) is arranged on the outer walls of the pipelines of the reaction gas sampling pipe (7) and the sample gas sampling pipe (8), and the temperature of the reaction gas and the sample gas entering the ionization region can be controlled between room temperature and 300 ℃.
8. The apparatus according to claim 1, wherein:
the reaction gas sampling tube (7) and the sample gas sampling tube (8) can be a metal capillary or a quartz capillary respectively, and can be one or a plurality of reaction gas sampling tubes; the length is 0.05-5 m, and the inner diameter is 25-500 mu m.
9. The apparatus according to claim 1, wherein:
the ionization source can work in two modes of photochemical ionization and photoionization, and can realize mutual switching by changing the voltages loaded on the repulsion ionization (2), the isolation electrode (3) and the ion focusing electrode (5) and the types of the reaction gases.
10. The apparatus according to claim 1, wherein:
the outer wall surface of the ultraviolet light source (1) is in airtight connection with the inner wall surface of the through hole, and the peripheral edge of the ionization source outlet electrode (6) is in airtight connection with the inner wall surface of the through hole A;
the reaction gas provided by the reaction gas source (12) is one or more than two gases with water vapor, methylene dichloride, dibromomethane, oxygen and nitric oxide, wherein the mass purity of the one or more than two gases is greater than 99.999% of nitrogen, argon, helium or other rare gases.
CN202111374926.3A 2021-11-18 2021-11-18 Zoned non-uniform field photoionization and/or photochemical ionization source Pending CN116137223A (en)

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